The present invention relates to an apparatus and a process for applying discrete portions of a web material onto a receiving web. The apparatus and process are particularly useful in the manufacture of disposable absorbent articles, including diapers, adult incontinence products, sanitary napkins and the like.
Manufacturing processes are often required to provide discrete strips of a material onto a continuous web, in such a way that the discrete webs of material are spaced apart along the length of the continuous web. Features manufactured in this way include either elastic or non-elastic strips: one example of an elastic strip is the elastic leg cuffs applied to diapers; one example of a non-elastic strip is the absorbent core of a diaper or sanitary napkin which is typically constructed from air-laid fibres.
It is known to provide an apparatus for applying discrete portions of a web material onto a receiving web by supplying elastic strips to transfer members in a supply zone, the transfer members being rotated about a central axis. The transfer members are moved radially outwardly and then, in a transfer zone, the elastic strips are applied to the receiving web so that the elastic strips are transferred from the transfer members and onto the receiving web.
U.S. Pat. No. 4,578,133, issued Mar. 25, 1986, discloses a method and apparatus for applying elastic strips to a moving web of material by means of transfer members which move at a first orbital radius through the supply zone and at a second orbital radius through the transfer zone. Optionally the transfer-members may also be radially pivoted by pivoting the transfer member about an axis transverse to its strip carrying surface.
However, when the apparatus of the prior art are operated at high speed the contact between the transfer elements, the elastic strips and the receiving web occurs over a very brief period of time, usually no more then several milliseconds. This results in difficulties in achieve good reliable transfer of the strips from the transfer elements on to the receiving web.
It is an objective of the present invention to provide an apparatus wherein the contact time between the transfer elements, the elastic strips and the receiving web is increased.
The invention provides an apparatus for applying discrete portions of a web material onto a receiving web, comprising:
a primary axis of rotation and an attachment zone at an average radial distance, R1, from the primary axis of rotation;
transfer elements rotatable about the primary axis, the transfer elements receiving a second web at a radial distance, R2, from the primary axis wherein the radial distance R1 is greater than the radial distance R2;
a means for displacing the transfer elements so that the second web is moved immediately adjacent to the attachment zone; and
an attachment surface rotatable about the primary axis and through the attachment zone, for transporting the receiving web about the primary axis, whereby discrete portions of the second web is attached to the receiving web in the attachment zone, forming a composite web comprising the receiving web and discrete portions of the second web.
The invention further provides a process for applying discrete portions of a web material onto a receiving web, comprising the steps of:
providing an attachment zone at an average radial distance, R1, from a primary axis of rotation;
providing a second web at a distance, R2, from the primary axis, whereby the radial distance R1 is greater than the radial distance R2;
displacing the second web at least in a radial direction relative to the primary axis so that the second web is displaced immediately adjacent to the attachment zone;
juxtaposing the receiving web and the second web in the attachment zone to form a composite web comprising the receiving web and discrete portions of the second web; and
transporting the receiving web about an arc of a circle, the circle having a primary axis and a first radius R1.